The present invention relates to a method of administrating authorization to control an image sensing apparatus in an image distribution system in which camera parameters (e.g., a pan angle, a tilt angle, and a zoom ratio) of the image sensing apparatus are controlled by a remote client via a network and input image signals from the image sensing apparatus are digitized and provided over the network so as to be displayed at the client side.
An image distribution system including a camera connected via a network, such as the Internet, in which an image sensed by the camera is transmitted to a plurality of clients of the image distribution system via the network so as to enable the clients at remote locations to observe the image has been developed.
Among such image distribution systems, a system which allows a client receiving an image signal from a camera, as an image sensing apparatus, to control the pan angle, tilt angle, and zoom ratio of the camera has been developed as a teleconference system, for instance.
The image distribution system of the present invention is based on such a system and allows one of a plurality of clients at a time to control the pan angle, the tilt angle, the zoom ratio, and so on, of a camera for a predetermined period of time, and requires the client to be certified and authorized to control the camera.
In such systems, when communication between the authorized client and the camera is undesirably terminated due to a problem in a communication path while the authorized client is controlling the camera, the authorized client has to repeat operations to gain certification and authorization all over again after the communication path is restored.
Recently, there are various ways to connect to the Internet, and some clients connect to the Internet via radio communication using, e.g., a portable telephone. Especially, when a client connects to the Internet via a wireless communication path, undesired termination of the communication is a problem which may frequently happen.
Further, many clients generally connect to a desired network only when they want to connect via the integrated service digital network (ISDN) or a modem, instead of being permanently connected. In such cases, it is not rare that a connection to the network is terminated for some reason.
In an image distribution system which issues authorization to control the camera to one client at a time for a predetermined period of time, when the communication between the authorized client and the camera is undesirably terminated during the predetermined time period, the right of the authorized client to control the camera for the predetermined period is infringed.
Further, if a money charging system to charge a client for the time to control the camera is adopted in the image distribution system, it is necessary to strictly administrate the authorized period and the charging of money, and a problem of how to charge for a period after sudden termination of communication during the predetermined authorization period arises since the client is not fully responsible for the termination.
Currently, the aforesaid problem is left unsolved, and when such a previously-authorized client tries to regain the authorization after the communication path is restored, the previously-authorized client is considered as a different client in most cases.
Further, by the time the previously-authorized client regains the authorization after the communication path is restored, there is a possibility that the camera has been controlled by another client using different control parameters (a pan angle, a tilt angle, and a zoom ratio) and the scene the camera is viewing is different from the scene where the previously-authorized client controlled the camera to view.
The present invention has been made in consideration of the above situation, and has as its object to, when communication between a client and a camera is undesirably terminated while the client possesses authorization to control the camera and the client restores a communication path within a predetermined period of time, allow the client to continue to control the camera under the same camera conditions as at the time of the undesired termination, thereby providing an image distribution system and method of controlling the image distribution system capable of controlling the overall system while taking troubles in communication into consideration.
According to the present invention, the foregoing object is obtained by providing an image distribution system comprising: an image sensing apparatus controllable by an external device; an image transmission apparatus having a function of digitizing and transmitting an image signal acquired by the image sensing apparatus via a network and a function of issuing authorization to control the image sensing apparatus; an image reception apparatus which receives and displays the transmitted digitized image signal, further requests to control the image sensing apparatus; and a network connecting the image transmission apparatus and the image reception apparatus, wherein, in a case where the image transmission apparatus issues the authorization to control the image sensing apparatus to the image reception apparatus and communication between the image reception apparatus and the image transmission apparatus is undesirably terminated while the image reception apparatus holds the authorization, by restoring the communication within a predetermined period, the image reception apparatus is allowed to continuously control the image sensing apparatus under the same conditions as at the time of the undesired termination.
Further, according to the present invention, the foregoing object is also obtained by providing a control method for controlling an image distribution system having an image sensing apparatus controllable by an external device, an image transmission apparatus having a function of digitizing and transmitting an image signal acquired by the image sensing apparatus via a network and a function of issuing authorization to control the image sensing apparatus, an image reception apparatus which receives and displays the transmitted digitized image signal, further requests to control the image sensing apparatus, and a network connecting the image transmission apparatus and the image reception apparatus, wherein, in a case where the authorization to control the image sensing apparatus is issued to the image reception apparatus and communication between the image reception apparatus and the image transmission apparatus is undesirably terminated while the image reception apparatus holds the authorization, the image reception apparatus is allowed to continuously control the image sensing apparatus under the same conditions as at the time of the undesired termination if the image reception apparatus restores communication within a predetermined period.
Furthermore, according to the present invention, the foregoing object is also attained by providing a computer program product comprising a computer usable medium having computer readable program code means embodied in the medium of a control method for controlling an image distribution system having an image sensing apparatus controllable by an external device, an image transmission apparatus having a function of digitizing and transmitting an image signal acquired by the image sensing apparatus via a network and a function of issuing authorization to control the image sensing apparatus, an image reception apparatus which receives and displays the transmitted digitized image signal, further requests to control the image sensing apparatus, and a network connecting the image transmission apparatus and the image reception apparatus, the product including computer readable program code means for, in a case where the authorization to control the image sensing apparatus is issued to the image reception apparatus and communication between the image reception apparatus and the image transmission apparatus is undesirably terminated while the image reception apparatus holds the authorization, enabling the image reception apparatus to continuously control the image sensing apparatus under the same conditions as at the time of the undesired termination if the image reception apparatus restores communication within a predetermined period.
Further, according to the present invention, the foregoing object is also attained by providing an image transmission apparatus, used in connection with an image sensing apparatus controllable by an external device, having a function of digitizing and transmitting an image signal acquired by the image sensing apparatus via a network and a function of issuing authorization to control the image sensing apparatus, wherein, in a case where the image transmission apparatus issues the authorization to control the image sensing apparatus to an external apparatus and communication between the external apparatus and the image transmission apparatus is undesirably terminated while the external apparatus holds the authorization, the image transmission apparatus allows the external apparatus to continuously control the image sensing apparatus under the same conditions as at the time of the undesired termination if the external apparatus restores the communication within a predetermined period.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.